Heaters for engines in various vehicles or vessels are well known. The purpose of these heaters is to pre-heat the vehicle engine by direct or indirect heating of the engine's oil or cooling liquid, such it starts easier in cold weather. Heaters for other mechanical units in a vehicle or vessels, such as gearbox, hydraulic system, transmission, are also known.
There are different types of engine heaters. One type comprises a compartment with an electric heating element placed inside. The compartment has an inlet opening and an outlet opening such that the engine's cooling liquid hose may be cut and the hose ends connected to these openings. The engine heater is thus a part of the engine's cooling circuit, and the cooling liquid is heated by the heating element and circulates in the engine's cooling circuit. Another type comprises an electric heating element which is inserted into the engine block, for example through a freeze plug and connected there, in order to heat the cooling liquid inside the engine.
A third type is a so-called contact heater, where an electrical heating element is mounted onto the engine (on e.g. the engine block or sump) and with an abutting surface in direct contact with a part of the motor, such that the liquids inside the motor (oil or cooling liquid) are heated by convection heat from the contact heater via the engine block wall. Contact heaters comprise generally an electric heating element, where the heating element in principle is an electric resistance which generates heat when it is subjected to an electrical potential. The heating element is usually cast inside an aluminium element which is configured to fit the geometry of the region of mounting, It is known to apply heat conducting paste to the heater's contact surface, in order to enhance heat transfer from the contact heater to the engine block or sump. The invention concerns a contact heater.
U.S. Pat. No. 2,838,648 describes a contact heater comprising a metal housing which is configured for mounting an engine crankcase. An electric, and manually controlled, heating element is arranged in a compartment in the housing.
One weakness associated with the known contact heaters is the risk of overheating, even if it has a thermal protection (which is not common in all heaters). This may lead to carbonizing of the oil and hence a deterioration of the oil's lubricating properties, For those heaters without a thermal protection, overheating may also occur if the heater is not properly mounted on the engine, gearbox, etc. Overheating may led to ignition and fire. It is also a disadvantage that contact heaters must be custom made for the specific motor type, gearbox, etc. in order for it to fit on the exterior geometry of the location where it is to be mounted. This results in that contact heaters often are more expensive to manufacture, than other types of engine heaters.
The invention provides solutions that mitigates some of the weaknesses associated with the known engine heaters, and provides additional advantages.